Power sensing comprises sensing voltage and current and multiplying to determine consumed power (P=I*V). A commonly employed technique for power sensing includes using a high precision discrete resistor connected in series with a power source. The current through the resistor causes a voltage drop across the resistor. Since the resistor value is known, the current may be represented by the voltage drop across the resistor. Power may be determined using an operational amplifier that multiplies current through the sense resistor and the source voltage. For source voltage sensing, an analog-to-digital converter (ADC) may be employed to convert the source voltage value to a digital format. If an ADC is used for both current and source voltage sensing, such digital values may be post processed by a microprocessor to determine power consumed.
Conventional power sensing techniques, however, suffer from numerous drawbacks. Complex circuitry with multiple stages including post processing by a microprocessor is typically needed for multiplying current and voltage. However, various sources of errors are still introduced by typical power sensing techniques. Conventional power sensing circuitry is typically characterized by high power consumption while providing poor speed performance and overall accuracy. More specifically, conventional techniques for sensing current across active or passive components create conflicting requirements between accuracy and low power dissipation across the components while conventional techniques for sensing source voltage are bound by the absolute voltage rating of the device process technology.
Improved power sensing techniques that do not have the shortcomings of existing techniques would be useful.